Project Summary/Abstract Astrocytes are the major regulators for energy storage, utilization and metabolic function in the central nervous system (CNS). Cocaine abuse and HIV infections are significant risk factors for disrupting brain energy metabolism and cocaine abuse is strongly associated with HIV-1 infection and a subsequent development of AIDS. The proposed research is aimed at investigating the effects of cocaine and HIV-Transactivator protein (HIV-Tat) on astrocyte energy metabolism and associated neuronal impairments. Altered DNA methylation in the region of the mitochondrial genome encoding the NADH dehydrogenase (NDH- displacement loop (D-loop) Family) subunits (ND1-ND6) plays a critical role in energy storage and utilization by regulating the energy source of brain metabolism to preserve CNS cell functions. Therefore, we investigated the role of cocaine and/or HIV-1 infection on the mitochondrial epigenetic mechanisms that alters the astrocytic energy metabolism. Moreover, the role of mitochondrial DNA methyl transferases (mtDNMTs) in impacting energy deficits in astrocytes leading to neuronal impairment has never been elucidated in the context of either cocaine or HIV-Tat, or in combination. Our preliminary studies showed that cocaine and/or HIV-1 Tat targets DNMTs and mtDNMTs (mtDNMT1, mtDNMT3A and mtDNMT3B) with concomitant activation of mitochondrial biogenesis in peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1?) that is known to regulate mtDNA synthesis and control energy metabolism affecting neuro plasticity and spine density. We thus hypothesize that cocaine acts as a co-factor in the neuropathogenesis of HIV-Tat by activating DNMTs expression in astrocytes leading to energy deficits and impacting DNA methylation and mitochondrial biogenesis. These epigenetic mechanisms are mediated by of 5-methylcytosine (5-mC), 5-hydroxymethylcytosine (5hmC) the regulatory D-loop region and its effect and ten-eleven translocation (TET) family dioxygenases , which affect energy transfer into neurons and dysregulate neuro plasticity, spine density and cell growth. Accordingly, in the specific Aim # 1A we will examine whether cocaine in association with HIV-Tat affect energy dysfunction of astrocytes and impacts DNMTs, mtDNMTs and biogenesis-led energy transfer, in Aim 1B# we propose to determine the effect on neuroplasticity/ axons/ dendrites formation and cell growth in primary neurons thereby contributing to neuronal death; the specific Aim # 2, we will validate the mechanistic study involving cocaine exposure of HIV-Tat (GT-tg) transgenic mice to investigate the mtDNMTs role in energy metabolism, and whether piracetam (a neuro-protective agent) treatment reverses the effects of cocaine and HIV-Tat on mtDNMTs leading to neuro plasticity and axons/ dendrites formation to develop a therapeutic strategy regulating energy metabolism impacting neurotoxicity. An understanding of cocaine and HIV-associated astrocytes energy deficits that lead to neurotoxicity will have translational significance for therapeutic targeting and controlling the energy metabolism in HIV-infected cocaine users.